The introduction of technology has changed how courtrooms function over the years. Courtroom AV has become quite sophisticated with electronic systems for recording, presenting evidence, case management, and remote appearances — just to name a few.
As part of the increased use of technology in courtrooms, the introduction of sound masking, or courtroom white noise, has been a significant addition to the trial process. In fact, within the past 20 years, notable improvements have been made in courtroom AV that help to speed trials.
In the past, if attorneys wanted to have a private conversation with a judge, they would either need to remove the jury to another room, or they themselves would have to move to a different room, like the judge’s chambers. However, with today’s improved AV technology, a judge is able to transmit masking noise over courtroom audio speakers with the touch of a button and cover a private sidebar conversation with the attorneys at the bench.
How is this possible? What types of noise mask conversations and which is the best to use in courtrooms? And, furthermore…
How does noise have a color?
As human beings, we often use analogies to help us understand foreign concepts by using more common ideas as comparisons. Because light and sound share the properties of a wave moving through the air, light (and color) creates a good analogy to help us classify the different types of random noise that we encounter. Just as different wavelengths of light make different colors, different wavelengths of sound make different tones.
For the base of this analogy, let’s begin with the color white. White light is a composition of all visible wavelengths (colors) being seen at the same time. Similarly, white noise is the composition of all audible wavelengths (tones) being heard at the same time. If this sounds like it would be a chaotic mix of sounds, you are right. White noise is commonly compared to the sound of tuning a radio to an unused AM frequency.
The different noises that are described below are mixtures of all the audible tones, however, the different “colors” are made by concentrating more energy at different areas of the frequency spectrum. When more energy is concentrated in the lower frequencies (longer wavelengths) we compare the noise to light with a longer wavelength, and vice versa.
Common colors of noise:
Black – as with light where black is the absence of all light, black noise is the absence of all sound frequencies. Black noise is the sound of silence.
White – as with light, white noise is all frequencies on the sound spectrum at once. White noise is often compared to the sound of static that is heard when a radio is tuned to an unused frequency.
Pink – a full spectrum of noise with more energy concentrated in the lower frequencies. Sounds like white noise with extra bass. Pink noise is often compared to crashing ocean waves.
Red (also called “Brownian” or Brown noise) – a deeper version of pink noise, full spectrum of noise with even more bass than pink noise. Often compared to the roar of a waterfall or heavy rainfall.
Blue – a full spectrum of noise with more energy concentrated in the higher frequencies (the inverse of pink noise). Often compared to the hiss of a water spray.
Violet (Purple) – a higher version of blue noise, full spectrum of noise with even less bass than blue noise. Sounds like an even higher hiss than blue noise.
Green – a full spectrum of noise with more energy concentrated in the middle frequencies. Often referred to as “background noise of the world”, as it resembles the ambient noise found in nature.
How does sound masking work?
To figure out which noise is best for masking sidebar conversations in a courtroom, first we need to think about how sound masking works.
A conversation is heard when the sound waves being created by a person’s voice hit the listener’s eardrums. In order to mask the conversation, audio that covers the sound waves of speech must be present. Rather than using a singular tone at a very high volume to cover the sound waves from the speaker, random noise can effectively mask conversations at a much lower volume.
By producing noise that incorporates many different tones (wavelengths) of sounds, the sound waves made by a person’s voice essentially get lost in the noise. It is important to understand that sound masking is effective over a specific distance. This distance is where the volume of the conversation and the volume of the masking noise are nearly equal. The amplitude (volume) of a conversation decreases over distance. Therefore, the volume of the masking noise determines the distance at which the sound masking is effective.
When participants of the conversation are in close proximity, their voices can easily be heard by one another despite the presence of the masking noise. However, a jury member who is much further from the conversation will only hear the masking noise as the sound waves from the conversation decrease in amplitude and get lost in the masking noise.
Which noise is best for a courtroom?
Typical human voices fall somewhere between 85 Hz and 3,000 Hz (3 kHz). This is an oversimplification but will do for our purposes here. Considering that the audible range for the human ear is roughly 20 Hz to 20,000 Hz (20 kHz), a noise with a higher energy concentration in the lower frequencies will best serve the purpose for masking a conversation.
Looking back at our noise descriptions, we see that pink and red noise concentrate more energy in the lower frequencies. Because of the way that the energy in pink noise drops off as the frequency increases, it very closely matches the way humans perceive sound in octaves. Therefore, pink noise sounds very balanced and is more pleasing to the ear.
Because pink noise is adept at masking conversations and fairly unobtrusive, it is the most common noise chosen for conversation masking in courtrooms.
Cutting Through the Noise
AV technology is integral to the function of an electronic courtroom. Thinking ahead to include options, such as conversation masking, is critical to the planning of the courtroom AV infrastructure.
At Nomad AV Systems, we can help you plan for the special considerations of thoughtfully integrating AV into your courtroom. With two decades of experience designing, installing and supporting courtroom AV solutions, Nomad has developed a thorough understanding of the technology required by courts.